Dr Lewis Dartnell, an astrobiologist at the Centre for Planetary Sciences in London, said: "If these organisms use arsenic in their metabolism, it demonstrates that there are other forms of life to those we knew of.

"They're aliens, but aliens that share the same home as us."

The space agency will announce the full extent of the findings at a press conference titled “astrobiology finding which will impact the search for evidence of extraterrestrial life”.

They believe the creature proves the existence of a second form of life that exists in tandem and before and after intelligent life blooms on planets across the universe.

It follows a growing belief that alien life far from being rare is actually abundant in the universe just in a form that is not recognisable as life.

At the heart of his theory is that life on earth may have come and gone many times during the planet's existence.

These creatures are the remnants of the previous inhabitants.

Scientists have also estimated that life of some kind exists on hundred billion trillion Earth-like planets in space.

However it is usually just bacteria and intelligent life such as us is fleeting and only exists for a fraction of the time.

A study last month said that the universe is teeming with planets capable of supporting alien life.

After studying stars similar to the Sun, astronomers found that almost one in four could have small, rocky planets just like the earth.

Many of these worlds may occupy the "Goldilocks" zone – the region where conditions are neither too hot, nor too cold, for liquid water and possibly life.

Planets outside our own solar system are too far away and too small to see directly with telescopes.